1. Field of the Invention
The present invention relates to an image recording apparatus, and more particularly, to an image recording apparatus including a line-type recording head unit formed by connecting a plurality of recording heads and capable of performing high-speed recording.
2. Description of Related Art
An image correction apparatus for use in an image recording apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2000-168109 (U.S. Pat. No. 6,287,027). This image correction apparatus is intended to be applied to an image recording apparatus having a recording head unit formed by disposing, contiguously in a main scanning direction, a plurality of recording heads each having a plurality of nozzles. When an image is recorded by this image recording apparatus, the recording head unit is scanned in a direction (subscanning direction) perpendicular to the main scanning direction in which a recording medium is fed. In this image correction apparatus, correction charts for a correction of mounting position errors of the recording heads, a correction of a density variation, and a color correction, respectively, are printed and respective corrections are performed on the basis of the printed correction charts.
In the meantime, in order to improve the operation speed and maintainability in conventional image recording apparatuses, an image recording apparatus has been proposed which includes a line-type recording head unit having a plurality of recording heads separated from each other in a direction of the width of recording medium. A specific example of such an image recording apparatus is a line-head ink-jet printer. In this image recording apparatus, nozzles serving as recording elements are disposed, at a pitch corresponding to the resolution on the recording apparatus, on each of the recording heads. In this image recording apparatus, when an image is recorded (printed), the line-type head unit including the plurality of recording heads and the recording medium are relatively scanned in a predetermined scanning direction.
The image correction apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2000-168109 cited above makes a correction of one-dimensional position errors of the recording heads in the direction (subscanning direction) in which recording elements of the recording heads are disposed and/or makes a correction of the recording density. However, Japanese Unexamined Patent Application Publication No. 2000-168109 does not disclose a technique of correcting two-dimensional recording position errors due to zigzag motion and/or vibrations in the feeding direction of a recording medium, a technique of correcting a density variation due to a change in paper feeding speed or due to a feeding speed variation or zigzag motion of a recording medium or due to head temperature, nor disclose a technique of correcting a change in an area in which overlapping of recording elements occurs between adjacent recording heads.
In the correction performed in the image recording apparatus using the line-type recording head unit having plural recording heads, it is required to make a correction of recording position errors over two-dimensional positions on a recording medium and/or make a correction of a two-dimensional density variation.